Pulpstone



Jan. 5, 17937. T LARSSON 2,066,629

PULPSTONE Filed March 25, 1936 3mm THL/RE L HRS-SUN Patented Jan. 5,1937 1 UNITED STATES PULPs'roNF.

Thure 'Larsson, Worcester; Mass, assignor to Norton Company, Worcester,Mass, a corporation of Massachusetts Application March 25, 1936, Serialo. 70,813

4 Claims.

The invention relatesto grinding wheels, and with regard to its morespecific features to a pulp grinding-wheel or stone for the grinding oflogs into fibre which is converted into pulp and thereafter made intopaper.

One objectof the invention is to provide a simple and practicalpulpstone construction. Another object of the invention is to provide anexpansible pulpstone construction embodied in a particular shape of thesegments or sectors. Anotherobject of the invention is to provide afreely cutting pulpstone. Another object of the invention is to providea segment or sector which is substantially non-fracturable. Anotherobject of the invention is to provide a simplified method for themanufacture of an expansible pulp-stone. Other objects will be in partobvious or in part pointed out hereinafter.

'I'he'invention accordingly consists in the features of construction,combinations of elements, arrangements of parts, and in the severalsteps and relation and order of each of said steps. to one or more ofthe others thereof, all as will be illustratively describedherein, andthe scope of the application of which will be indicated in the followingclaims;

Inthe accompanying drawing, in which is shown one of severalpossible-embodiments of the mechanical features of this invention,

- 5 Fig. '1 is an elevation of a pulpstone;

Fig. 2 is a' fragmentary radial sectional view, on an enlarged scale,taken on the line 2-2 of Fig. 1;

' Figx3' is an isometric view of a segment or sector. v

' Referring'first to Figures 1 and 2, there is provided a driven spindlel0 to'which is keyed the hub, not 'sh6wm of 'a drum l2, and theconstruction in this respect may be the same as disclosed in U.SsLetters Patent No. 1,850,231 issued on application of Wallace W.Greenwood. I preferably provide Wedge blocks 20, studs 22 and nuts 23 asin the aforesaid Greenwood patent.

Considering now more particularly certain specific features of myinvention, and referring particularly to Figure 3, I provide a pluralityof sectors 25 (parts of this general type being sometimes referred to assegments). Each sector 25 has a flat or plane side 26 which, togetherwith others, forms one radial face of the entire wheel. Each sector 25has a face 21 originally in an axial plane of the Wheel but having V-grooves 23 cutting its surface leaving dihedral angle apexes 29 whichare in said original plane.

The surface soformed is also altered by one-half of a dovetailed groove30.

Referring now to Figures 1 and 2, the side 3| opposite the side 21 ofeach sector has V-grooves 32 leaving dihedral angle apexes 33 which arein the original radial axial plane of the sector. Whereas the apexes 29are radial lines, the apexes 33 are not radial but parallel to the wheelaxis. When two sectors are put together, therefore, apexes 29 crossapexes 33. More specifically, they are perpendicular to each other, butit must be understood that they might cross each other at differentangles with similar results so far as this invention is concerned. Theradial axial side 3! is modified by the other half 35 of a dovetailedgrove. The wedge blocks 20 are dovetailed andrest against oppositegrooves 30, 35 and against facings or shoes 36, 31 respectively and holdthe sectors in position, as described in the aforesaid Greenwood patent.

Considering now Figure 1, I prefer to stagger the line joining sectorsin the manner illustrated in order that there shall not be a circle onthe wheel surface which is entirely in a line of division. In otherwords, any circle in a plane normal to the wheel axis on the surface ofthe wheel passes over solid abrasive.- Accordingly, considering nowsectors individually, and referring again to Figure 3, I provide twoside faces 40 and M; the planes of which are not perpendicular to thewheel axis and the planes of which are disposed to each other to form avery obtuse dihedral angle. The surface 40 is grooved by V- grooves 42having apexes 43 which are substantially radial." The surface 41 isgrooved by V- grooves 44 having apexes 45 which are perpendicular toadjoining apexes 43 on a different sector, but again contiguous apexes43 and 45 may cross each other at other angles.

Considering now the manufacture of the sectors 25, I provide a quantityof abrasive grain, for example fused alumina, emery or corundum, orsilicon carbide or any other desired type. I provide a quantity ofsuitable bond, preferably ceramic bond intending to include preformedfrits and the like. Forming a desired mixture of the abrasive grains andbond, preferably coating each granule with some bond, and including inthe mixture a suitable plasticizer or temporary binder, or using aplastic clay such as ball clay and a certain amount of water, I place aregulated quantity of the mixture in a mold which is shaped to form asector in outline, that is to say with the two cylindrical surfaces, theplane surface 26 and surfaces 21, 3|, 40 and 4| to true planes,

but with the half dovetailed grooves 30 and breaking said planes. Ipress the mixture in the mold, preferably to a predetermined volumecontent of abrasive grains and bond and to the described shape, and uponremoving the mass from the mold it is in the so-called "gree conditionand by reason of the temporary binder or plasticizer or plastic clay orall of these will hold its shape. I then form the grooves 28, 32, 42 and44 by means of gang milling cutters, or shaping tools or like operationsanalogous to a machining operation on metal.

After the grooves are formed as described, the sectors are placed in akiln and the bond is burned or otherwise treated to convert it to thedesired condition. In the case of ceramic bonded articles I use anysuitable type of kiln and kiln temperatures. In the case of organicbonded articles, the heat treating or maturing temperature may bedescribed as a baking rather than a burning or firing. It must beunderstood that the wheel may be formed of sectors bonded with any typeof bond and is not limited to any particular one. For example, rubbermay be used, or phenolic resinoids or other types of resinoids. Shellacor sodium silicate may also be used. Various cements have been foundsatisfactory for the manufacture of pulpstones and I may use any onethereof. But so far as certain features of the invention are concerned,I prefer to use a fired ceramic or a vitrified bond, and certainadvantages follow from the use thereof.

After the wheel is assembled, it may be used in the usual manner for thegrinding of logs to form pulp. While various fillers may be placedbetween sectors, one characteristic of my invention is that the stonemay be used without any filler. After a short period of pulp grinding,the spaces between sectors become filled with a packing of wood pulp, atleast to some extent. Furthermore, the absence of any foreign materialbetween sectors has certain advantages, and the relatively open spacebetween sectors (filled only with a deposit of wood pulp which has anegative action on wood) provides an open clearance space whichfacilitates cutting. Furthermore, sectors may readily be replaced with aminimum of difiiculty.

Pulpstones are preferably made to withstand ordinary conditionsinvolving use in practically Arctic localities, at least so far astemperature is concerned, and a particular pulpstone may have towithstand a change from a temperature of minus 20 or 30 F. to atemperature of several hundred degrees Fahrenheit. During the normaloperation of grinding pulp, no such high temperatures are usuallyreached, but occasionally the supply of water is cut off accidentallyand the pulpstone rapidly overheats. Furthermore such heating is notuniform throughout the stone. As a result thereof there is an expansionwhich, unless provision is made, may fracture sectors and may ruin thestone.

According to the present invention, when excess expansion occurs, theapexes 29, 33, 43 and 45, or some or all of them, are crushed.Contacting apexes crush each other, especially owing to the crossedarrangement. This constitutes a safety feature to prevent fracture ofthe sectors under unusual conditions. When the emergency is over and thestone has cooled off, there is simply a little wider gap between sectorswhich will rapidly fill up.

I may provide one set of grooves and apexes resting against a plane faceof an adjacent sector in certain cases, as where mixtures are usedresulting in sectors of less grade hardness. With the describedconstruction, however, there is substantially point contact and theapexes crush before the sectors can fracture.

It will thus be seen that there has been provided by this invention amethod and an article in which the various objects hereinabove set forthtogether with many thoroughly practical advantages are successfullyachieved. As various possible embodiments might be made of themechanical features of the above invention and as the art hereindescribed might be varied in various parts,

all without departing from the scope of the invention, it is to beunderstood that all matter hereinbefore set forth or shown in theaccompanying drawing is to be interpreted as illustrative and not in alimiting sense.

I claim:

l. A grinding wheel comprising a drum, 9. plurality of sectors attachedto said drum, and radial faces of some sectors being grooved so thatcrushable apexes are provided at all joints.

2. A grinding wheel comprising a central support, sectors attached tothe central support, some sides of some sectors being grooved to providecrushable apexes.

3. In a grinding wheel, a central support, a plurality of sectorsattached to said central support, radial sides of adjacent sectors beinggrooved leaving apexes, and the apexes being disposed to cross eachother.

4. In a grinding wheel, a drum, a plurality of sectors each having onehalf of a dovetailed groove, bolts and wedge blocks to attach thesectors to the drum, there being a plurality of rows of sectors soshaped that the joint between rows is a staggered line, each sectorbeing grooved leaving apexes, and the apexes running in difl'erentdirections so that each set of apexes contact apexes running acrossthem.

THURE LARSSON.

